jlbell

Just curious what y'all think of this:

It only happens on a cold engine, after bringing the rpm up to 4000 and letting it go back to idle, and last only a few minutes after starting the car. It almost acts likes it based on how warm the cats are or until a vacuum is built up. Not really sure if it should be a concern, but it made me laugh the first time I heard it, so I figured y'all would like to hear it.

Pothole5000

Could be some lose catalyst in the cats, that settles down once it's it up to temp.

jlbell

Yea there is a bit of noise that comes from the center of the car upon start-up sounds like popcorn popping, but goes away when warmed up.

MP4.2+6.0

Suggestion: get under the car when it/exhaust is cold and tap on each converter with a rubber mallet or something similar. If it rattles, you have your issue figured out.

You can go for full replacement of course, or a used one. Or, the old cheap method is to drill a hole or two into it sufficient to drive some stainless sheet metal or similar screws. The screws hold the honeycomb of the catalyst in place if it has broken free internally so it doesn't rattle. As long as overall exhaust noise isn't objectionable and it can pass smog, it works. I did so on my 1985 Audi 5000 as it got older and it likewise come down with a temperature related rattle. Lasted for rest of life of car.

jlbell

Going to do the screw method once I have a lift! Im just always concerned that it has something to do with the engine.

mishar

Your exhaust have a small hole (for now). Fix it and it will stop making that sound.